1. Field of the Invention
The present invention relates to a vehicle lighting unit, and more particularly to a vehicle lighting unit which controls a lighting unit such as a headlamp which illuminates the front of the vehicle, a tail-lamp or the like which is fixed to a vehicle.
2. Description of the Related Art
A headlamp is disposed at the front of the vehicle to improve the visibility of the front of a driver at night or the like. Further, in order to let other vehicles know the existence of the vehicle of the driver, tail lamps are fixed to the rear of the vehicle. Further, in order to improve the visibility of meters or the like for informing the driver of a vehicle speed or a fuel consumption at night or the like, the meter, or the like are illuminated. These illuminations are switched on/off by operating lighting (illumination) switches.
In recent years, in order to solve the annoyance involved with switching operation of the illumination switches, such a type of lighting unit as described below has been generalized. This lighting unit has an illumination sensor for metering the brightness of the vehicle exterior. The lighting unit judges whether or not the illumination value metered by the illumination sensor is equal to or less than a predetermined illumination value, and thereby judges whether or not the outside of the vehicle is dark. When the outside of the vehicle has been judged to be dark, headlamps or the like are switched on automatically.
If the value metered by the illumination sensor is equal to or less than a predetermined illumination value, when the headlamps are switched on automatically, there may be caused a problem as will be described below. Namely, in a case in which the vehicle exterior becomes bright/dark intermittently at a place such as a tunnel or the like or at the lower portion of a bridge beam or the like where lighting windows are disposed so as to be spaced apart from each other at a predetermined distance, because the vehicle exterior becomes light/dark intermittently, a headlamp or the like may be switched on/off. In this case, the switching on/off of the headlamp is carried out in a passing state.
In order to solve this problem, Japanese Patent Application Laid-Open (JP-A) No. 5-147469 discloses a headlamp light control apparatus in which, when the illumination value metered by the illumination sensor varies intermittently within a predetermined time, the switching on of the headlamp can be delayed.
However, in a prior art, because the switching on/off of the headlamp is delayed in the case in which the value metered by the illumination sensor varies intermittently within a predetermined time, when a vehicle has traveled at dark portions for a predetermined period of time or more, it means that a predetermined period of time has already passed. In this case, since the illumination value metered by the illumination sensor cannot be judged to vary within a predetermined period of time, the headlamp is switched off without delaying the switching-ON time. After the headlamp has been switched off, when the vehicle again enters into a dark portion, the headlamp is switched on immediately. Accordingly, because the time during which the lamp is switched off is very short, the driver may be annoyed with this.